The packaging industry uses a wide variety of films and containers prepared from various thermoplastic resins and compositions for packaging food and non-food products. These packages provide adequate protection (for example, protection from mechanical damage, barriers to air or moisture, etc.) of the product contained within until the consumer is ready to use the product. It is also desirable for the package to be designed to allow the consumer easy access to the product at the appropriate time. Often, packages consist of rigid containers made from metal (particularly aluminum), paper, fiberboard or plastic (for example, polypropylene, crystallized polyethylene terephthalate (CPET) and high-impact polystyrene (HIPS)) with a lidding film sealed to the container. It is desirable that the seal between the container and the lidding film provide a strong hermetic seal to protect the product and that the seal is easily and cleanly peeled by the consumer.
Common compositions used for sealants for lidding include compositions comprising polypropylene, polyethylene, ethylene vinyl acetate copolymers (EVA), ethylene/(meth)acrylate copolymers or amorphous polyester. They can also contain fillers or additives for achieving an easy peel characteristic. Many compositions comprising polyolefins are currently used for peelable heat seals in packaging applications because of their good processability, low cost, and adequate adhesion for many applications. However, these compositions are not sufficiently robust for all applications. For example, many packages are refrigerated or frozen to help preserve the product therein, and it is desirable to retain seal strength in cold temperatures. Also, polyolefin compositions (for example, those that contain EVA) have limited heat resistance that restricts their ability to be processed at high temperatures.
Therefore, it is desirable to develop compositions that provide improved performance than currently provided by commercially available sealants.